How to Get Music into Match My Sound: Scanning Sheet Music

Match My Sound™ uses the open source notation software MuseScore to render the sheet music. It means that one can upload notation files that are either in MuseScore or MusicXML format. The latter can be exported from most notation programs. When you happen to have the music on paper then there are basically two options:

Type the music into an engraving program

Use Music OCR (optical character recognition) applications

The first option has been the only choice for many musicians and it is the most time consuming one. The second option has been available for years but it seems like until very recently the performance of those apps was not what one would expect. It's probably individual, but having tried those products over the years I feel that the moment where I really started to save time by using the Music OCR tools was quite recently.
So what are the programs that I use? There are two:

The first one is cool because it has two in one: it both scans the music with the device's camera and then recognizes the notation which can be exported as MusicXML. It also costs a fraction of the price of its competitors. PhotoScore, in turn, is a powerful tool for even the most complicated scores, including handwritten. Use any scanner to get the PDF into PhotoScore.
There are more products that can do the job. The Midnight Music Podcast episode How to Scan Music by Katie Wardrobe mentions some of them.